1. Field of the Invention
The present invention relates to a reversible ratchet-type wrench. In particular, the present invention relates to a ratchet-type wrench that allows reversible operations without the risk of movement of a switching member for switching the ratcheting direction.
2. Description of the Related Art
Wrenches are an important hand tool and have many types such as spanners, adjusting wrenches, combination wrenches, and socket wrenches. Ring spanners are very useful when the fastener to be tightened/loosened is located in a difficult-to-access place. However, the ring spanners could not be operated in a reverse direction and thus require troublesome disengagement of the ring spanner from the fastener and reengagement of the ring spanner until tightening/loosening of the fastener is achieved.
U.S. Pat. No. 6,220,123 to Chen issued on Apr. 24, 2001 discloses a structure of a ratchet wrench comprising a ratchet wheel mounted in a circular opening of a wrench head of a common ratchet, and a cavity is provided in the circular opening adjacent to one side of the rod body of the wrench for mounting a restrictive teeth structure. The end terminal of the cavity is provided with a ball hole to contain a spring and a steel ball, and the restrictive teeth structure is urged by the steel ball to thereby control the high-torque movement of the ratchet wheel. A rotating disc is used to cover the opening and includes ratchet teeth for meshing top ratchet teeth of the restrictive teeth structure. However, the formation of top and bottom ratchet teeth on a side of the restrictive teeth structure would not be easy, and this decreases the torque-bearing capacity of the ratchet wrench, as the meshing area between the restrictive teeth structure and the ratchet wheel is reduced. Further, the restrictive teeth structure could not be reliably positioned, as there is no positioning means provided between the rotating disc and the wrench body. As a result, the rotating disc moves together with the restrictive teeth structure when the ratchet wrench turns freely. Further, since the top ratchet teeth of the restrictive teeth structure meshes with the ratchet teeth of the rotating disc and the bottom ratchet teeth of the rotating disc meshes with the ratchet teeth of the ratchet wheel, the ratchet wrench must be disengaged from the fastener before switching of the ratcheting direction through rotation of the rotating disc. Further, the engaging force between the ratchet wheel and the rotating disc provided by a C-shaped fastening ring was found to be poor. As a result, the ratchet wheel and the rotating disc could fly away from the wrench body when the ratchet wrench is subject to a relatively high torque.
FIGS. 16 and 17 of the drawings illustrate a conventional wrench comprising a handle 21′ and a head 20′ extended from the handle 21′. A hole 22′ is defined in the head 20′ and a compartment 23′ is defined in a wall defining the hole 22′. A transverse groove 24′ is defined in a side of a web portion between the handle 21′ and the head 20′. A spring 61′ and a ball 62′ are received in a receptacle 25′ defined in a bottom wall defining the transverse groove 24′. A drive member 30′ is rotatably mounted in the hole 22′. Two pawls 40′ are slidably mounted in the compartment 23′ and connected by a spring 43′. A switching member 50′ is slidably engaged in the transverse groove 24′ and includes a U-shaped portion 52′ that is located in an overlapped portion between the transverse groove 24′ and the compartment 23′. The overlapped portion is designed to expose the peg 42′ on each pawl 40′, allowing the switching member 50′ to move the pawls 40′. The ball 62′ is biased by the spring 61′ to selectively engage with one of three retaining holes 53′ of the switching member 50′ such that the teeth 41′ of one of the pawls 40′ is engaged with the teeth 33′ of the drive member 30′, thereby switching the ratcheting direction of the wrench. However, the overlapped portion results in a thin wall thickness (L) of the head 20′, which adversely affects the torque-bearing capacity. A solution for increasing the torque-bearing capacity is to increase the wall thickness (L) of the head, yet this requires a deep transverse groove 24′ and a thick switching member 50′ as well as dovetail engagement between the transverse groove 24′ and the switching member 50′ for avoiding disengagement therebetween. This would increase the difficulty of manufacture. Further, the U-shaped portion 52′ of the switching member 50′ and the overlapped portion of the transverse groove 24′ and the compartment 23′ are exposed such that alien objects may enter the compartment 23′ and thus cause malfunction of the wrench.
FIGS. 18 and 19 illustrate another conventional wrench comprising a handle 1″ and a head 11″ extended from the handle 1″. A hole 14″ is defined in the head 11″ for rotatably receiving a drive member 2″. A transverse hole 12″ having an open end is defined in a web between the handle 1″ and the head 11″. A spring 4″ and a ball 5″ are received in a receptacle defined in a peripheral wall defining the transverse hole 12″. A pawl 3″ having two toothed sections 31″ is slidably mounted in the transverse hole 12″ and then sealed by a cap 9″. A substantially T-shaped switching member 8″ includes a horizontal section 81″ outside the head 11″ for manual operation and a threaded vertical section 82″ extending through a slot 13″ in the web into a screw hole 33″ in the pawl 3″. Thus, the pawl 3″ is moved in the transverse hole 12″ when the switching member 8″ is moved. The ball 5″ is biased by the spring 4″ to engage with one of two retaining grooves 32″ of the pawl 3″ such that one of the toothed sections 31″ of the pawl 3″ is engaged with the teeth of the drive member 2″, thereby deciding the ratcheting direction of the wrench. However, the cap 9″ is apt to be disengaged from the transverse hole 12″. The movement of the pawl 3″ is limited if the cap 9″ is mounted in a deeper position for avoiding disengagement. The threaded vertical section 82″ of the switching member 8″ and the screw hole 33″ of the pawl 3″ result in difficulty in manufacture and assembly. The threaded vertical section 82″ of the switching member 8″ tends to be disengaged from the screw hole 33″ of the pawl 3″ after a period of time, and the wrench malfunctions accordingly.